I was just curious to know why the A-300B4 with the original GE engines make that high pitch sound that seems to go from low to high to low to high on approach a few miles out. I have heard several make this sound and tonight I heard an Aero Union A300B4 make that pitchy sound a few times on approach to LAX a few miles out and it made me ask this question. DC10-30's and 747-200's with the similiar GE's don't make that characteristic sound on approach, thanks.